WASHINGTON :The U.S. National Highway Traffic Safety Administration said on Thursday that it is opening an investigation into 2.88 million Tesla vehicles equipped with its Full Self-Driving system over more than 50 reports of traffic-safety violations and a series of crashes. The auto safety agency said FSD - an assistance system that requires drivers to pay attention and intervene if needed - has "induced vehicle behavior that violated traffic safety laws."  The agency said it has reports of